Pancreatic cancer is the fourth and fifth leading cause of cancer-related death for men and women, respectively, following lung, colon, and prostate cancers in men and lung, breast, colon, and ovarian cancers in women. Patients usually present with advanced disease, making treatment difficult. Surgery is the only curative therapy, yet local disease recurrence with or without spread to distant organs occurs in over 80% of patients. Attempts at better therapeutic modalities are necessary in order to improve outcome in this disease.
Frequently, neoplastic transformation leads to alterations in the expression of various polypeptides in tumor cells. For example, certain mucins and mutated forms of K-ras oncogene polypeptides are overexpressed in 90% of pancreatic ductal adenocarcinomas (hereinafter referred to as “PDA”), and have been targets for therapeutic interventions. To date, however, vaccines that target these polypeptides have not been particularly successful clinically. Vaccines have failed to generate long-term immune memory, likely due at least in part to tumors adapting in ways that allows them to escape immune recognition and killing. Several agents that can modulate immune tolerance have been tested clinically, but with only modest responses, perhaps due to an insufficient amount of the agents reaching the tumor site and/or because the agents themselves have been associated with unwanted side effects such as can result from their binding to normal cells.
Additionally, it is a major challenge in oncology to not only treat a patient's primary disease, but also to prevent the occurrence of metastases. It is currently believed that metastatic disease could result from the migration of tumorigenic cells, frequently referred to as tumor stem cells or cancer stem cells, from the primary tumor site to other sites, where they can infiltrate the site and form new tumors (see e.g., Bonnet & Dick, 1997; Reya et al., 2001; Al-Hajj et al., 2003; Pardal et al., 2003; Dontu et al., 2004; Singh et al., 2004; Brabletz et al., 2005). As a result, it would be beneficial to be able to identify and eliminate these cells should they be present in a patient.